What should the vacuum readings be for a 351 with a 204/214 cam at idle? What is typical? What would cause low readings, besides a leak?

should be between 18-20 inches at idle with that small of a cam.
Low readings could be caused by retarted cam timing, or retarded ignition timing.

worn rings, worn out valve seats.

worn rings, worn out valve seats.That's what I'm thinking. The valves are all new(less than 1000 miles) but rings are questionable. If the rings were worn, wouldn't it be burning oil, though? It runs like it has a vacuum leak(crappy idle) but I can't seem to find one. Blew a whole can of carb cleaner at it and nothing changed.

whats yolur initial timing set at?
is the orriginal timing chain and gears still in it?

new timing chain and 12* of timing with a new msd box
and dizzy.Adjusting the timing up or down doesn't change anything.

compression test?

compression test?
yup compression test time.

how low are we talking?

run a dry test, then squirt some oil or atf in the hole and do it again. if your comp goes up, rings.

X3, worn rings don't necessarily mean burning oil as your oil ring may still be in tact.

Do a compression and then a leakdown test to figure out where you are at. If you're below 120 as an average, I would start considering a rebuild. My guess is you have a cylinder or two below 100 lbs and all the others are high giving you a crappy idle.

Did you get it hot? As in did the temp gauge surpass the 235* mark? If so, stop all this testing, your motor is cooked.

Did you get it hot? As in did the temp gauge surpass the 235* mark? If so, stop all this testing, your motor is cooked.


dunno if this quilifies for that but my engine has seen shall we say 250 plus a few times and nearly always ran 210-220 on the highway. IT still runs great and definatly has more power than I should have put into it.

I say that because stock gauges often have some error in them when they get into the higher temp. range. Often times an engine can survive to 250* and slightly higher with stock style cast pistons. The problems indicated sound very much like an engine that got hot and has a few cylinders low on compression.

If you have forged pistons you have to be extremely careful as most engines are only toleranced to withstand growth to a certain temperature. Anything over 235* on a forged motor and you've likely scored the pistons.

I have autometer guages, so I know they are pretty accurate. ;)